The reverse of a $2$-digit integer is the integer obtained by reversing the order of the $2$ digits. For example the reverse of $43$ is $34$. How many $2$-digit positive integers $N$ exist with the property that the sum of $N$ and the reverse of $N$ is the square of an integer?
extremely confusing integer question
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combinatorics
integers
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0the problem is i do not undertand the q, so i havent rried anything – 2017-01-24
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0well i attempted to label the first digit x, and the second y, however i figure that that wont work – 2017-01-24
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1$65+56=121$ which is a perfect square ($11^2$). You are asked to find all numbers with the same property. – 2017-01-24
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0As an aside, I would not say this is an extremely confusing question. You may be extremely confused, but the question is clearly stated. – 2017-01-24
1 Answers
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Hint: let the integer be $\overline{ab}=10a+b$ where $1 \le a,b \le 9$ are its decimal digits (assuming $a,b \ne 0$ so that both numbers have, in fact, two digits). Then: $$\overline{ab}+\overline{ba}= 10a+b+10b+a=11(a+b)$$ Now, for $11(a+b)$ to be a perfect square, $a+b$ must be a multiple of $11\,$, so $\cdots$